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Microb Pathogenisis
| Question | Answer |
|---|---|
| What is a pathogen? | an organism able to cause disease |
| virulence | degree of pathogenicity, invasiveness and toxigenicity, and degree and nature of host cell involvement |
| What is a virulence factor? | • Pathogenic traits in bacteria are due to the action of genes coding for specific structures and substances |
| virulence mechanisms of microorganisms | resistance, production, evasion, induction and adherence |
| What is adherence to host cells? | – extracellular bacteria use receptor-mediated attachment to cell surface - using specific adhesin molecules; may be on structures: pili or fimbriae – viruses and intracellular bacteria use specific receptors as prelude to entering the cell |
| What is invastion of host cells? | • penetrate or be taken up by host cell • provides access to nutrients (bacteria) and host cell machinery (viruses) • may help in avoidance of immune response |
| production of substances released.... | degradative enzymes and toxins |
| What are exotoxins? | secreted into the environment, protein based; highly antigenic, several modes of action, produced by gram positives and gram negatives, very specific |
| What are endotoxins? | • LPS in outer membrane of gram negatives….can damage cell directly, pore formation and cytoskeletal modulator. Disrupt cell communication and interfere with internal cell processes |
| Siderophores | • iron-binding compounds excreted by pathogens under iron stress • host actively sequesters iron during infection to limit growth of pathogens |
| Host immune response to pathogen | • superantigen • cross-reacting antibodies • immune complexes • inflammation • endotoxic shock |